Tumors manifesting mainly at the pediatric age or manifesting only at this stage are known as childhood tumors. For this reason, they are also sometimes referred to as pediatric tumors. In the context of the present invention, the term childhood tumor or pediatric tumor will be used interchangeably.
The group of childhood tumors includes neuroblastomas (NBs), ganglioneuroblastomas (GNBs) and ganglioneuromas (GNs), forming the group of neuroblastic tumors (NTs). Neuroblastic tumors are the most common solid extracranial childhood tumors that develop from neural crest cells which have already been compromised during peripheral nervous system formation, so they are localized in the adrenal medulla or in the ganglia of the paravertebral sympathetic chain. Most localized NBs, GNBs and GNs have excellent survival rates, but today metastatic NBs have survival rates of about 40% despite being subjected to intensive multimodal therapies.
Neuroblastic tumors are a group of highly heterogeneous tumors from the clinical, anatomopathological, genetic and biological viewpoint. The biological bases responsible for the clinical diversity of NTs are only partially known, but they are without a doubt behind the different ways in which tumors respond to treatment protocols. Among them, ploidy alterations, unbalanced translocations, recurrent chromosome region deletions or additions and MYCN oncogene amplification, stand out. These genetic-molecular alterations can hardly be modified therapeutically although they are crucial for the biological behavior of NTs. Before describing them further, it was already known that highly differentiated NTs with a higher proportion of Schwann-type stromal component (NB in differentiation, GNB and GN) were associated with a better prognosis than undifferentiated NBs. Some of the molecular pathways responsible for cell differentiation processes in NT have been discovered. These pathways are of great therapeutic importance since they can be pharmacologically modulated. Therefore, for example, retinoic acid induces differentiation in NB cell lines and in patient tumors, improving overall survival of a patient sub-group. Some NBs are resistant to the action of this drug, but the lack of in-depth knowledge about the molecular mechanisms responsible for NT differentiation complicates the design of new differentiating agents that can benefit a large number of patients.
The calcium sensor receptor gene (CASR) was cloned in 1993 from bovine parathyroid cells and is part of the C family of the G protein-coupled receptor (GPCR) superfamily, along with eight glutamate receptors, two GABA-B receptors, some taste receptors and GPRC6A amino acid sensor. This family of receptors detects signals from ions, amino acids and nutrients, among others, and transmits them to the intracellular medium. They all share a similar structure consisting of a large extracellular amino-terminal domain, seven transmembrane helices and an intracellular carboxyl-terminal tail. In the case of CASR, its main function is to detect the fluctuations of extracellular Ca2+ and accordingly regulate the secretion of parathyroid hormone (PTH) in parathyroid glands and calcitonin in thyroid C cells, which hormones are responsible for normalizing calcemia. In the context of the parathyroid, CASR activation by calcium translates into a drop in parathyroid hormone (PTH) regulation and production, which will in turn reduce plasma calcium concentration to keep it within a narrow margin (1.1-1.3 mM).
CASR expression has been found in different neoplasias with the particularity that they attribute very different, even opposing functions, thereto in different tumor contexts. Therefore, for example, it has been described that CASR activation promotes prostate carcinoma proliferation and metastasis, whereas data seems to support that it participates in colon carcinoma differentiation processes.
There are direct CASR agonists (or type 1 agonists) and allosteric activators of CASR (or type 2 agonists). Direct CASR agonists such as Ca2+, Mg2+, Gd3+, neomycin, L-amino acids, activate CASR by means of direct interaction with the extracellular domain thereof. In contrast, allosteric activators do not activate the receptor per se but rather change its three-dimensional structure, such that it becomes more sensitive to the calcium stimulus. Cinacalcet is an allosteric activator of the calcium sensor receptor. U.S. Pat. No. 5,688,938 describes several CASR agonists, such as NPS R-467 and NPS R-568, NPS R-568 (also referred to as R-568) being the most active. Likewise, U.S. Pat. No. 6,296,833 describes the use of calcium agonists or antagonists for the treatment of cancer. The present application describes the use of cinacalcet for the preparation of a pharmaceutical product for the treatment of neuroblastic tumors. Surprisingly, the use of cinacalcet results in significant advantages because it is capable of inducing tumor cell apoptosis at a lower concentration than other CASR agonists.